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Ways to Add 2 Digit and 1 Digit Numbers

Main Core Tie

Mathematics Grade 1
Strand: NUMBER AND OPERATIONS IN BASE TEN (1.NBT) Standard 1.NBT.4

Time Frame

3 class periods of 45 minutes each

Group Size

Large Groups

Authors

DAPHNE MARCHANT

Summary

Adapted from a lesson in Math Expressions. Students practice three strategies for adding 2 digit and 1 digit numbers.


Materials

  • Pencils and paper or mini-whiteboards and markers
  • Large paper and markers
  • Headings to cut out (attached)
  • Scissors and glue


Background for Teachers

Understanding of strategies for adding

  • Count on with fingers
  • Draw all with sticks and circles
  • Count on with sticks and circles


Student Prior Knowledge

Understanding of how to count on with fingers and how to represent two digit numbers using (tens) sticks and (ones) circles


Intended Learning Outcomes

  • Students will use three different strategies for adding two-digit and one-digit numbers.
  • Students will create an infographic showing their three strategies.


Instructional Procedures

  1. Review counting on with fingers by "putting a number in your head," then "putting the other number on your fingers" and counting on (e.g. say 79 and touch forehead, then hold up 4 fingers and count 80, 81, 82, 83).
  2. Using pencil and paper or mini-whiteboards, review representing 2 digit numbers with sticks and circles. (e.g. 79 = lllllll ooooo oooo)
  3. Use the sticks and circles strategy to show adding numbers and combining ones to show new groups of ten (see sample infographic for example). Practice on paper/ whiteboards until students are comfortable with this strategy.
  4. Instead of drawing the 2 digit number, write it in numeral form, then count on using circles and making new groups of ten (see sample infographic for example). Practice on paper/ whiteboards until students are comfortable with this strategy.
  5. Group students into groups of 2-3. Assign each group a problem like 79+4. Have each group make a poster showing how to solve their addition problem using all three strategies previously practiced. Give each group a copy of the headings to use on their posters but let them decide how to best show the strategies.


Strategies for Diverse Learners

  • Gifted: Use two 2-digit numbers or one 3-digit number
  • Struggling: Use single digit numbers, assign student to work with a partner for extra practic, and or allow student to use a 100 chart to count
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Assessment Plan

  • Assess posters using attached rubric
  • Assess individual mastery using attached quiz


Rubrics

Created: 01/12/2015
Updated: 02/03/2018
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